How to Identify a person thru an email?

Last few nights I have received multiple "FaceTime" calls to my iPhone, from a random email ending in @optonline.net
Iv never heard of this apparently it's part of optimum… But the point is how can I track down the email to an owner or get any information. Who ever it is knows me and is threatening my daughter and I.
Please any help on how I can get some information of who it is, until then the police can't get a restraining order they need a name first. And again they called thru FaceTime so all I have is the email address. I can't get anything else from the call and they never show there face and the voices are distorted but I believe are female.

You can't. You will never identify them.

Report as spam or phishing and move on.

All you can do is be alert for scams.

Try googling the name. People stupid enough to do that are also stupid enough to post their email address all over the place in connection with their name. You should also block the email if fact time allows it.

Unfortunately, the only way you could ever do that would be to have the provider of this person's email account search and provide you with that information. Which they will NEVER do without a court order. The only way you could get a court order would be to convince a judge that this person's threats are eminent and pending. Which would be extremely difficult to prove. Also, since a warrant has to be assigned to a specific person, the courts can't order the service provider to do a random search without violating other customers' rights.

You are stuck in a no win situation.

The only thing you can do is do some old-fashioned detective work and ask your daughter, and possibly her friend, questions that can lead you to the culprit. If you can get a name of a possible suspect, you can then file a police report and have them look into it. If they suspect that this person is making threats, they can get a search warrant to find out his/her email address and see if there's a match.

So, you would first have to come up with a name to find the email. You can't work the other way around.

Unless, you have a friend that works at the service provider that would be willing to illegally do a search for you and provide with the name. Which would allow you to go to the police with a suspect's name and follow the procedure I mentioned before. But, you couldn't use the information directly to get any legal action.

You can report it to your service provider. They may be able to block the email for you. You could also just deactivate the FaceTime through the settings.